Publication Date:
2015-01-08
Description:
The Weddell Sea Anomaly (WSA) is a recurrent feature of the austral summer mid-latitude ionosphere where electron densities are observed to maximize during the local nighttime. In this study, tidal decomposition is applied to FORMOSAT-3/COSMIC total electron content (TEC) and electron density observations between 2007–2012, to quantify the components dominating local time and spatial variation in the WSA region. Our results present some of the first three dimensional space-borne analyses of the WSA from a tidal perspective over multiple years. We find that the features of the WSA can be reconstructed as the result of superposition between the dominant diurnal standing (D0), eastward wavenumber 1 (DE1), westward wavenumber 2 (DW2), and stationary planetarywave 1 (SPW1) components in TECs, producing the characteristic midnight WSA peak. The D0, DE1, DW2, and SPW1 components are found to be an interannually recurring feature of the southern mid- to high-latitude ionosphere during the summer, manifesting as enhancements in electron density around 300 km altitude of the summer mid to high magnetic latitudes. The phases of the aforementioned nonmigrating diurnal signatures in electron density in this region are near evanescent, suggesting in-situ generation, rather than upward propagation from below. However, the SPW1 signature shows some signs of an eastward tilt with altitude, suggesting possible downward propagation. The relation of these components to possible generation via in-situ photoionization or plasma transport along magnetic field lines is also discussed using results from the GAIA general circulation model, connecting the tidal interpretation of the WSA to previously examined generation mechanisms.
Print ISSN:
0148-0227
Topics:
Geosciences
,
Physics
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